The present invention relates to a mobile wireless apparatus used in a car telephone, a portable telephone, or the like, and particularly relates to a mobile wireless apparatus in which electric power consumed during standing-by operation can be saved.
FIG. 1 shows the configuration of a conventional mobile communication apparatus.
As shown in FIG. 1, a conventional mobile wireless apparatus has a reception system constituted by a reception circuit 2 for converting a signal received by a reception antenna 1 into a signal of a predetermined frequency and a predetermined amplitude, a demodulation circuit 8 for demodulating the signal converted by the reception circuit 2 to obtain a base-band signal, and a speaker 13 for reproducing the base-band signal obtained by the demodulation circuit 8. The conventional mobile wireless apparatus further has a control system constituted by an error detection and correction circuit 12 for detecting bit errors in the digital signal in the base-band signal obtained by the demodulation circuit 8 and for correcting the bit errors, a sequence control circuit 11 for controlling connection to a base station on the basis of the output signal from the error detection and correction circuit 12, and a timing control circuit 10, connected to the sequence control circuit 11, and for controlling the timing of the whole mobile wireless apparatus. The conventional mobile wireless apparatus further has a transmission system constituted by a modulation circuit 7 which is supplied with a signal obtained by multiplexing an audio signal from a microphone 14 and a signal from the error detection and correction circuit 12, and a transmission circuit 5 for converting the output from the modulation circuit 7 into a signal of a transmission frequency and for transmitting the signal through an antenna 6.
The conventional mobile wireless apparatus further has a synthesizer 4 for selecting a reception frequency and a transmission frequency. The synthesizer 4 is controlled by the timing control circuit 10 and supplies a high-frequency output to both the reception circuit 2 and the transmission circuit 5.
The timing control circuit 10 is connected to the reception circuit 2, the demodulation circuit 8, the sequence control circuit 11, the error detection and correction circuit 12, the synthesizer 4, and the like, in order to perform an intermittent receiving operation and is further connected to points necessary for timing control.
The operation of the conventional mobile wireless apparatus having the aforementioned configuration will be described hereunder.
A reception signal received by the antenna 1 is converted into a signal of a predetermined frequency and a predetermined amplitude in the reception circuit 2 by using the output from the synthesizer 4. The signal of the predetermined frequency and amplitude is fed to the demodulation circuit 8, in which a base-band signal is reproduced and sent out as a voice through the speaker 13.
On the other hand, a digital control signal in the base-band signal reproduced by the demodulation circuit 8 is supplied to the sequence control circuit 11 after error correction in the error detection and correction circuit 12. While controlled by the sequence control circuit 11 and the demodulation circuit 8, a timing control signal during intermittent reception of a predetermined interval and during communication, as shown in FIG. 2, is generated in the timing control circuit 10.
As shown in FIG. 2, during intermittent reception, the timing control circuit 10 intermittently powers on only the reception circuit 2, the demodulation circuit 8, the sequence control circuit 11, the error detection and correction circuit 12 and the synthesizer 4 so as to carry out reception of the control signal.
As shown in FIG. 2, during communication, not only the reception system is operated continuously but a signal obtained by multiplexing an audio signal from the microphone 14 and the digital control signal from the error detection and correction circuit 12 is supplied to the modulation circuit 7 to modulate a carrier wave. After being converted into a signal which has a predetermined frequency and predetermined electric power through the transmission circuit 5 by using the output from the synthesizer, the carrier signal is transmitted through the antenna 6.
Electric power consumed in the period of standing-by can be saved even in the conventional mobile wireless apparatus having the aforementioned configuration because the control signal can be received intermittently as shown in FIG. 2.
The conventional mobile wireless apparatus, however, has a problem in that a battery is wasted because the intermittent reception is repeated even in the case where the wireless apparatus is out of its service area, or even in the case where the electric source is left on in spite of the fact that the wireless apparatus is in an unreceivable place such as a basement of an office building.